Sokushi to Hametsu no Saijaku Majutsushi

Ark and Leanne are aspiring adventurers. Upon appraisal, Leanne is revealed to be on the level of a hero, with the level cap of 80 and the skills [High Priestess], [Goddess' Protection], and [Holy Magic]! However, Ark has an instant death magic with a level cap of... 1?! With his instant death magic, he'll becomes embroiled in a national crisis that shakes the world!